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# Plantar interossei

The plantar interossei are three muscles under the outer metatarsals that bring the toes together.

Official name: Plantar interossei muscles

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## What it is

Three muscles under the third, fourth and fifth metatarsals.

## What it does

Bring the toes together and help bend the toes at the base.

## Key points

- Three unipennate muscles, each from a single metatarsal (3–5); they adduct toes 3–5 toward the [axis](https://durgical.com/en/anatomy/axis/) of the [second toe](https://durgical.com/en/anatomy/second-toe/)
- Fourth (deepest) layer of the sole, with the dorsal interossei and the [fibularis longus](https://durgical.com/en/anatomy/fibularis-longus-muscle/) and [tibialis posterior](https://durgical.com/en/anatomy/tibialis-posterior-muscle/) tendons
- Supplied by the lateral plantar nerve; with the lumbricals they bend the MTP joints and keep the toes straight

## Key facts

**Origin**
Three unipennate muscles from bases and medial sides of metatarsals 3–5

**Insertion**
Medial sides of bases of proximal phalanges of toes 3–5

**Action**
Adduct toes 3–5 toward second toe (PAD); flex MTP joints

**Nerve**
Lateral plantar nerve (S2–S3)

**Blood supply**
Plantar metatarsal arteries (plantar arch)

## Relations

**Above**
Dorsal interossei and metatarsals 3–5

**Below**
[Adductor hallucis](https://durgical.com/en/anatomy/adductor-hallucis/), the deep plantar arch with the deep branch of the [lateral plantar nerve](https://durgical.com/en/anatomy/lateral-plantar-nerve/), and the long flexor tendons

**Course**
Their tendons pass forward, dorsal to the deep transverse metatarsal ligament, to the medial side of the proximal phalanges

## How to find it

They cannot be felt. In dissection they appear in the fourth layer once the long flexor tendons and adductor hallucis are removed; on coronal MRI they lie on the plantar side of the lateral metatarsals.

## On imaging

Not seen on radiographs. On MRI they lie in the deepest layer of the sole along the plantar side of metatarsals 3 to 5; short-axis images separate them from the dorsal interossei. Fatty atrophy of the interossei and other intrinsic foot muscles suggests a lateral plantar nerve lesion or a peripheral neuropathy such as diabetic neuropathy.

## Common problems

- Like the other small muscles of the foot, it can weaken with age, nerve problems or tight shoes, which can let the arch drop or the toes change shape.

## Clinical notes

- Ischaemic contracture after foot compartment syndrome involving the interosseous compartments can leave claw toes
- Lateral plantar nerve lesions weaken them with the other interossei, leading to clawing

## Memory aid

"PAD": Plantar ADduct. The [big toe](https://durgical.com/en/anatomy/great-toe/) and second toe have none: the big toe has adductor hallucis and the second toe is the axis.

## Test yourself

Think of the answer, then tap the question to see it.

## What are the origin and action of the plantar interossei?

Three unipennate muscles from metatarsals 3–5; they adduct toes 3–5 toward the second toe («PAD») and flex the MTP joints.

## Which nerve supplies the plantar interossei?

The lateral plantar nerve.

## Why do the big toe and second toe have no plantar interosseous?

The big toe has the adductor hallucis, and the second toe is the axis of movement.

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Educational information, not medical advice. For any symptom, see a health professional.

## Its names

**Official Latin (TA2)**
musculi interossei plantares TA2 2687

**Official Spanish (DeCS)**
Músculos interóseos plantares

**English (TA2)**
Plantar interossei muscles

**Also called**
plantar interossei muscles 1-3

## Related

- [Dorsal interossei](https://durgical.com/en/anatomy/dorsal-interossei-muscles-of-foot/)
- [Lateral plantar nerve](https://durgical.com/en/anatomy/lateral-plantar-nerve/)
- [Plantar arteries](https://durgical.com/en/anatomy/medial-plantar-artery/)
- [Third metatarsal](https://durgical.com/en/anatomy/third/)
- [Fourth metatarsal](https://durgical.com/en/anatomy/fourth/)
- [Fifth metatarsal](https://durgical.com/en/anatomy/fifth/)
- [Third toe](https://durgical.com/en/anatomy/third-toe/)
- [Fourth toe](https://durgical.com/en/anatomy/fourth-toe/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Bony Pelvis and Lower Limb, Foot Muscles](https://www.ncbi.nlm.nih.gov/books/NBK539705/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/plantar-interossei-muscles/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/plantar-interossei-muscles/